The present invention relates generally to the art of welding power supplies. More specifically, it relates to welding power supplies having an output inductor.
There are a wide variety of welding processes and welding power supplies. Welding power supply or system as used herein includes one or more of the following components: a wire feeder, a power source or source of power, a torch or gun, a wire feeder controller, and a power source controller to control the various components (it may also exclude some of these components, such as the power source).
Many known welding power supplies have a power source followed by an output inductor (or choke). Output inductor, as used herein, includes an inductor between the switches that control the power and the welding output. The inducting effect (inducting, as used herein, includes inducing a magnetic field when current flows) of the output inductor lowers di/dt, thus generally smoothing the output, and maintaining and stabilizing the arc.
However, when the arc is being initiated a high di/dt is desired. The output inductor, which lowers di/dt, has the undesired effect of inhibiting or slowing arc-starting. Accordingly, many prior art welding power supplies provide a second winding on the inductor core.
One such prior art welding power supply is a Miller DeltaWeld(copyright), and a diagram of the main and auxiliary inductor windings is shown in FIG. 1. A power source 101 provides power through an inductor winding 103 to a welding output 105. Power source, or source of power, as used herein, includes the power circuitry such as rectifiers, switches, transformers, SCRs, etc that process and provide the output power.
An auxiliary inductor winding 107 is in magnetic communication, but not electrical communication, with inductor winding 103. A mechanical contactor 109 is in series with the ends of auxiliary winding 107, such that when closed, contactor 109 shorts auxiliary winding 107.
Inductor winding, as used herein, includes a winding that induces a magnetic field when current flows therein. Magnetic communication, as used herein, includes a magnetic connection wherein a magnetic field influencing one winding, influences the other winding. Electrical communication with, as used herein, includes a connection wherein electrical signals and/or power may be provided or received.
The arrangement helps start an arc because contactor 109 is closed when arc-starting, and opened after the arc is established (current is detected to determine the arc-state). The common core shared by windings 103 and 107 cause a voltage to be induced across winding 107 (when contactor 109 is closed) and a resultant current to flow. The B-field produced by the current flowing in auxiliary winding 107 will be in opposition to the flux produced by the weld current flowing in inductor winding 103. This counteracting flux re-balances, to some extent, the core to zero flux (neglecting exciting current) and thereby greatly reduces the effect of the iron core material. This results in a substantial reduction of inductance at the start, and a substantial increase in di/dt.
However, there will occasionally be difficulty in starting the arc even with the shorting winding. Accordingly, it is desirable to provide a system for welding that provides easier starting, preferably by providing an increased di/dt.
Another shortcoming of the prior art is that the output inductor has a constant value. Some welding processes would benefit from a variable output inductance, so that the di/dt may be controlled consistent with desired changes in the welding output. Accordingly, it is desirable to provide a system for welding that provides a variable output inductance.
According to a first aspect of the invention a welding-type power supply includes a power source, a welding output, an inductor winding and an auxiliary winding. The inductor winding is in electrical communication with the power source and the welding output. The auxiliary winding is in magnetic communication with the inductor winding, and in electrical communication with the power source and the welding output.
According to a second aspect of the invention a welding-type power supply includes a power source, and a welding output. An inductor winding and an auxiliary winding are in electrical communication with the power source and the welding output. The auxiliary winding is not in magnetic communication with the inductor winding.
A switch is in electrical communication with the auxiliary winding, a controller with a control output is connected to the switch, and/or the auxiliary winding is anti-parallel with the inductor winding in various embodiments. The controller may include an arc-state circuit with an output that is the control output.
According to a third aspect of the invention a method of initiating a welding arc includes providing welding-type power to an inductor winding and to an auxiliary winding in magnetic communication with the inductor winding. The welding-type power is provided from the inductor winding and the auxiliary winding to a welding output. Welding-type power is not provided to the auxiliary winding after an arc is established.
According to a fourth aspect of the invention a method of initiating a welding arc includes providing welding-type power to an inductor winding and an auxiliary winding. The auxiliary winding is not in magnetic communication with the inductor winding. Welding-type power is provided from the inductor winding and the auxiliary winding to a welding output. Welding-type power is no longer provided to the auxiliary winding when an arc is established. The presence and absence of at least one of an arc and an output short circuit is sensed in an alternative embodiment.
According to a fifth aspect of the invention a welding-type power supply includes a power source and a welding output. A variable inductance inductor is in electrical communication with the power source and the welding output.
The inductor includes an output winding and an auxiliary winding, both in electrical communication with the power source and the welding output and/or the auxiliary winding is in magnetic communication with the output winding in various embodiments.
The system includes a switch in electrical communication with the auxiliary winding, and may includes a capacitor in series with the switch and the auxiliary winding, in other alternatives.
The auxiliary winding is anti-parallel with the output winding in yet another embodiment
Other principal features and advantages of the invention will become apparent to those skilled in the art upon review of the following drawings, the detailed description and the appended claims.